Mapping Geothermal Vegetation with Hyperspectral and Thermal Imaging – A New Way to Explore Geothermal Areas

Abstract

Vegetation reflects activity of a geothermal system, through interactions between soil-chemical conditions, heat and gas emissions. Some plant species are extremely capable of thriving in such environments, such as kanuka (i.e. kunzea ericoides var. microflora), an endemic shrub of geothermal areas in the Taupo Volcanic Zone (TVZ), New Zealand. Remote sensing studies have targeted vegetation vigour on active geothermal areas, which can provide a fast and cheap surface exploration method as well as monitoring. In this study, airborne hyperspectral and thermal data has been acquired over the Waiotapu Geothermal Field, New Zealand to detect spatial distributions of kanuka, selected from a supervised classification. To the areas detected as kanuka a variety of vegetation indices (including Normalised Difference Vegetation Index, Simple Ratio Index, Red Edge Normalised Difference Vegetation Index, Vogelmann Index) were applied giving an insight to the overall health of kanuka in the Waiotapu Geothermal Field. The vegetation indices and the thermal infrared image spatial distributions were analysed by visual interpretation and quantitative analysis. This combined methodology allows to interpret the correlations kanuka plant has with geothermal heat flux, and therefore a path to utilise kanuka shrub as a proxy to detect active geothermal systems from a remote sensing platform.